PROJECT SUMMARY Idiopathic pulmonary fibrosis (IPF), a rapidly progressive, fatal lung disease with a median survival of less than three years post diagnosis, is more prevalent in aging population. Glycolysis, a critical pathway in glucose metabolism plays an important role in regulating host responsiveness to fibrotic lung injury. Recent studies reported that IPF patients exhibit higher glycolytic activity in fibrotic areas represented by high [18F]-2-fluoro-2- deoxyglucose (FDG) uptake in positron emission tomography (PET) scanning. We have demonstrated that fibrosis development is enhanced with aging and that increased glucose transporter 1 (GLUT1)-dependent glycolysis contributes to enhanced fibrogenesis in aged lung. Identifying the downstream and upstream mechanism by which GLUT1 regulates fibrogenesis is essential next step. For downstream mechanism we have shown that non-canonical TGF?1 signaling may be the pathway by which GLUT1-dependent glycolysis contributes to lung fibrosis. For upstream mechanism we have illustrated that age-dependent proteasome dysfunction might underlie enhanced GLUT1 protein expression. In this proposal we hypothesized that decreased proteasome function contributes to impaired GLUT1 degradation, which in turn activates signaling pathways to reinforce or modulate downstream cellular responses and thereby contribute to increased GLUT1- dependent glycolysis and fibrogenesis in aged lung. Aim 1 will investigate the upstream regulation of GLUT1 expression and age-dependent lung fibrosis by the ubiquitin-proteasome system (UPS) by using genetic and pharmacologic approaches to inhibit UPS in our two murine fibrosis models (bleomycin-induced lung injury and TGF?1 overexpression model). Aim 2 will investigate the downstream mechanism of GLUT1-dependent glycolysis and fibrosis development in lung. We will compare the extent of lung fibrosis observed in wild type, GLUT1 knockout, and GLUT1 overexpressing mice during bleomycin- and TGF?1-induced fibrosis models. Aim 3 will use human IPF cohort to define the levels of GLUT1 expression and their roles as a biomarker in patients with two distinct IPF phenotypes. This may translate into information useful to understand the complex interaction between GLUT1-dependent glycolysis and fibrosis, and provide a potential explanation for why older people are more susceptible to fibrotic lung disease. Results from our current studies may support the development of therapies for IPF based on targeting GLUT1 and/or its upstream/downstream regulators.